1. Technical Field of the Invention
The present invention relates generally to tire condition monitoring apparatuses or systems.
More particularly, the invention relates to a direct-type tire inflation pressure sensing apparatus that includes a transceiver provided on a wheel of a vehicle, a receiver provided on the body of the vehicle, and a transmitter provided on the body of the vehicle for determining the position of the transceiver relative to the receiver so as to ensure reliable transmission of a tire inflation pressure signal from the transceiver to the receiver.
2. Description of the Related Art
Conventional direct-type tire inflation pressure sensing apparatuses generally include a transmitter and a receiver.
The transmitter is directly installed to a wheel of a vehicle and includes a pressure sensor working to sense an inflation pressure of a tire mounted on the wheel. The transmitter is configured to send out a pressure signal representative of the inflation pressure of the tire sensed by the pressure sensor.
The receiver is installed to the body of the vehicle and includes an antenna. The receiver is configured to receive the pressure signal from the transmitter through the antenna and determine the inflation pressure of the tire based on the received pressure signal.
Specifically, with reference to FIG. 13, the transmitter J2 is placed inside the tire J1 and attached to an air valve J4 of the wheel J3. Consequently, when the vehicle is running, the position of the transmitter J2 relative to the antenna of the receiver varies due to rotation of the transmitter J2 with the tire J1, thus resulting in variation in the level of the pressure signal received by the receiver.
There may exist such a position of the transmitter J2 relative to the antenna of the receiver where the level of the pressure signal received by the receiver is lower than a necessary level. When the transmitter J2 is rotated to this position and sends out the pressure signal representative of the inflation pressure of the tire J1, the receiver cannot accurately recognize or identify the pressure signal, thus resulting in a decrease in the fidelity of the receiver.
To avoid such a decrease in the fidelity of the receiver, one may consider applying one of the following two conventional approaches.
The first approach is to determine a suitable installation position of the antenna of the receiver on the body of the vehicle such that the receiver can accurately recognize the pressure signal sent out by the transmitter J2 at any angular positions.
However, determination of such an installation position of the antenna requires an additional task of evaluating the level of the pressure signal received by the receiver.
Moreover, since the pressure signal sent out from the transmitter J2 will be attenuated during the course of transmission to the receiver, it is, indeed, very difficult to determine such an installation position of the antenna.
For example, when the transmitter J2 sends out the pressure signal at a position where the transmitter J2 is opposed to the receiver with the wheel J3 positioned therebetween, the pressure signal cannot pass through the wheel J3 that is generally made of a metal material.
Especially, when the maximum level of the pressure signal sent out by the transmitter J2 is restricted under regulations, determination of such an installation position of the antenna becomes more difficult.
Furthermore, in the case that the receiver has only a single antenna, through which the receiver receives all the pressure signals sent out from a plurality of transmitters J2 installed to different wheels J3 of the vehicle, it is required to install the antenna at an optimal position where the receiver can accurately recognize all the pressure signals sent out from different transmitters J2. However, determination of the optimal position is even more difficult, and a lot of time is required to evaluate the level of all the pressure signals received by the receiver.
The second approach is to allow the transmitter J2 to consecutively send out a plurality of frames, which contain the same pressure signal representative of an inflation pressure of the tire, so as to increase the probability of accurate recognition of the pressure signal by the receiver.
However, this approach still cannot certainly ensure accurate recognition of the pressure signal by the receiver.
Moreover, since a plurality of frames are sent out for transmission of a single pressure signal, the electrical power consumed by the transmitter J2 is increased. As a result, when the transmitter J2 is supplied with electrical power by a battery, the life of the battery will be shortened.